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Market data is available on the dedicated KalshiMD session. It supports order book snapshots and incremental updates for margin markets. Subscriptions are identified by Symbol<55>. KalshiMD does not support message retransmission. Use ResetSeqNumFlag<141>=Y on Logon.

Message Flow

Market Data Request (35=V)

TagNameTypeRequiredDescription
263SubscriptionRequestTypeCharY0=Snapshot, 1=Snapshot plus updates, 2=Disable previous snapshot plus update request
146NoRelatedSymIntegerCNumber of 55=Symbol entries in the repeating group that follows. Required for 263=0 and 263=1. For 263=2, the listed symbols are unsubscribed; omit to cancel all of the session’s subscriptions.
55SymbolStringCRepeating group field. The margin market tickers to subscribe to or cancel.
Example snapshot request
8=FIXT.1.1|35=V|49=your-api-key|56=KalshiMD|263=0|146=1|55=BTC-PERP|
Example snapshot-plus-updates subscription
8=FIXT.1.1|35=V|49=your-api-key|56=KalshiMD|263=1|146=1|55=BTC-PERP|
Example cancel a symbol
8=FIXT.1.1|35=V|49=your-api-key|56=KalshiMD|263=2|146=1|55=BTC-PERP|
Example cancel all subscriptions
8=FIXT.1.1|35=V|49=your-api-key|56=KalshiMD|263=2|

Market Data Snapshot Full Refresh (35=W)

Sent in response to a snapshot request and immediately after a snapshot-plus-updates subscription is accepted. Correlate by Symbol<55>.
TagNameTypeRequiredDescription
55SymbolStringYMargin market ticker.
268NoMDEntriesIntegerYNumber of book levels.
269MDEntryTypeCharYRepeating group field. 0=Bid, 1=Offer
270MDEntryPxPriceYBook level price in dollars.
271MDEntrySizeQuantityYBook level size in contracts.
Example snapshot response
8=FIXT.1.1|35=W|49=KalshiMD|56=your-api-key|55=BTC-PERP|268=2|269=0|270=19.5000|271=10.00|269=1|270=19.5100|271=5.00|

Market Data Incremental Refresh (35=X)

Sent after a subscribed market’s aggregated book levels change or a trade occurs. Correlate by Symbol<55> on each entry.
TagNameTypeRequiredDescription
268NoMDEntriesIntegerYNumber of market data entries.
279MDUpdateActionCharYRepeating group field. 0=New, 1=Change, 2=Delete.
55SymbolStringYRepeating group field. Margin market ticker.
269MDEntryTypeCharYRepeating group field. 0=Bid, 1=Offer, 2=Trade
270MDEntryPxPriceYPrice in dollars.
271MDEntrySizeQuantityYSize in contracts.
Example incremental update
8=FIXT.1.1|35=X|49=KalshiMD|56=your-api-key|268=1|279=1|55=BTC-PERP|269=0|270=19.5000|271=15.00|
Example trade update
8=FIXT.1.1|35=X|49=KalshiMD|56=your-api-key|268=1|279=0|55=BTC-PERP|269=2|270=19.5000|271=3.00|

Market Data Request Reject (35=Y)

Sent when a market data request cannot be accepted. Unknown market tickers are not currently rejected; the server sends an empty snapshot if it has no order book for the requested symbol.
TagNameTypeRequiredDescription
281MDReqRejReasonCharNReject reason.
58TextStringNHuman-readable rejection detail.

Common Reject Reasons (281)

  • 2=Insufficient bandwidth, including request or session symbol limits
  • 4=Unsupported SubscriptionRequestType